So… here is what you do. Go in to Garageband and create a 30 second clip of whatever you like for a ringtone. Songs in your itunes library, effects, a voice going Awooga Awooga!. Whatever.
Then .. select Export Song to Disk from the Share menu.

Export it to the Desktop for convenience. You will see a file with your filename and the extension .m4a – Click once on the file and once again to change the filename. Change the .m4a extension to .m4r and hit enter. You will be asked if you meant to do this.

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